The present invention relates generally to self-heating meal assemblies and more particularly to a novel self-heating group meal assembly.
Self-heating meal assemblies of the type used, for example, by the military to heat rations of food for an individual are well-known.
One example of a self-heating meal assembly designed for use for an individual is described in commonly-assigned U.S. Pat. No. 5,220,909, which issued Jun. 22, 1993, with inventors Pickard et al. In this patent, there is disclosed a self-heating individual meal assembly (also referred to as a "self-heating individual meal module") which includes a tub for holding a quantity of food to be heated. Below the tub is a tray containing an electrolytic-solution-activatable exothermic-chemical pad and a pouch containing an electrolytic solution. The tub is welded to the tray and is in contact with the pad. A pull-tab is attached to the pouch for opening the pouch so that the electrolytic solution inside the pouch can flow out to trigger the exothermic reaction in the pad so as to heat the tub containing the food. The tub and the tray are removably seated in a first paperboard carton which provides protection during storage and transportation and insulation during the heating process. The self-heating individual meal module may also include a second paperboard carton having removably seated inside a quantity of shelf-stable bread, a beverage powder, a dessert, accessories and eating utensils. The two paperboard cartons may be glued together to provide a complete single serve meal.
Another such self-heating meal assembly is described in U.S. Pat. No. 4,559,921, which issued Dec. 24, 1985, with inventor Benmussa. In this patent, there is disclosed a self-heating receptacle comprising a vessel for food to be heated, and below the vessel a sealed container containing two chemicals, e.g. quick lime and water. A sealed pouch within the container prevents one of the chemicals from contacting the other. A tearing filament secured to the pouch simultaneously opens the pouch and the container thereby triggering the exothermic reaction to heat said food vessel. The pouch is suspended by its ends above the bottom of the container and is surrounded by said other chemical. There is an outer housing in the bottom of which the container is disposed, the food vessel being disposed in the top of this housing. The container is hermetically sealed with a lid. The tearing filament extends across the lid below the bottom of the food vessel and emerges from between the housing and the food vessel in a portion that can be grasped by the user to pull on the tearing filament thereby both to open the pouch and to tear the lid.
While the above-described self-heating meal assemblies are generally well-suited for heating individual meal rations, they are not as well-suited for heating group meal rations, which are typically 12-36 times larger than individual meal rations. This is in large part due to the bulk of heating materials necessary to heat such large quantities of food. For example, measurements have shown that the heater to food weight ratio is typically 1:1 for packages utilizing quick lime as the solvent-actuable heating element and 1:8 for packages utilizing Mg-Fe as the solvent-actuable heating element. Consequently, to heat 26 pounds of food, one would typically require 26 pounds of quick lime or 3.5 pounds of Mg-Fe in addition to other packaging weights. These weights may be contrasted to current catering methods which use chafing trays and only a few ounces of a gelled alcohol.
Self-heating meal assemblies of the type described above also often encounter problems of shelf stability. More specifically, self-heating packages that use quick lime are known to slowly deactivate over time due to the hydroscopic nature of the material. Consequently, expensive steps, such as moisture barrier packaging, are often taken to hermetically contain the heater. Nevertheless, such techniques are not foolproof, and some moisture may still leak around necessary protuberances, such as pull tabs. Similarly, Mg-Fe heaters are typically packaged with salts and surfactants necessary for the heater to work, but these additives attract moisture and can slowly deactivate the heaters. More importantly, the safe transportation and storage of Mg-Fe heaters is problematic since the accidental water immersion of bulk packages could cause the heaters to react releasing flammable hydrogen gas.
Notwithstanding the above, there are many situations in which self-heating group-sized meal assemblies would be useful. For example, in military applications, it would be highly desirable to serve a meal to a large group without needing burners, fuel, heater cabinets or insulated carriers. In addition, there are also civilian applications including catering or meal service at group functions, particularly where fire codes do not permit open flames. Moreover, there are civilian applications for contingency operations in remote areas such as fire fighting or for disaster relief where there is no available food equipment or electric power.
In "Innovative Concepts for Self-Heating Meals," Activities Report and Minutes of Work Groups & Sub-Work Groups of the R&D Associates, Vol. 44, No. 1, pp. 35-39 (1992), published by the RESEARCH and DEVELOPMENT ASSOCIATES for MILITARY FOOD and PACKAGING SYSTEMS, INC., San Antonio, Tex., Pickard et al. describe the following concept for a Self-Heating Group Meal (SHGM): "The SHGM is an adaptation of the current institutional pouch. This pouch is constructed of a trilaminate similar to a Meal Ready to Eat (MRE) entree pouch. The institutional pouch typically holds 6.6 pounds of thermostabilized food, similar to a tray pack. This pouch is an excellent choice for chemical heating, because the packaging conducts heat well, the food cross-section is relatively thin, and there is no head space, so the pouch can be effectively heated on both sides.
"A polypropylene heating/serving tray has been configured for the pouch. The bottom of the tray holds six 30-gram heaters that require 12 oz. of water to activate. A typical meal would consist of a stack of four pouches and trays. Water is poured into a fold-out reservoir above the trays and is evenly distributed to the four trays through a tube. To conserve energy, the bottom tray sits on an insulating pad, and the entire meal is packaged in a plastic-lined, corrugated fiberboard box.
"To activate the SHGM, the box is opened exposing the reservoir. One canteen of water is poured into the reservoir and the box is re-closed. Preliminary testing has yielded remarkable time/temperature profiles that indicate this ration will heat-up the requisite 100.degree. F. from 40.degree. F. to 140.degree. F. in less than 30 minutes and will stay hot for 6 hours or more. Tests show that 6.6 pounds of water were heated from 50.degree. F. to 160.degree. F. in only 15 minutes.
"Because the SHGM is made from polymeric materials, the final package is expected to be very compact, light, and inexpensive. Reheating time and temperature can be controlled by design instead of by instruction. For example, a heater tray designed for chicken stew may have six 30 g pads. With regard to battlefield disposal, the polymeric materials can be burned or compacted to a small volume. The self-heating serving tray will also continue to keep the meal warm until the last soldier is served. Best of all, the pouches do not require can openers.
"Bulk packaging has been another consideration in the design. Cases (10.times.12.times.15 inches) will yield three levels of 16 cases on a standard 40.times.48 inch pallet. If the levels are designated for breakfast, lunch and dinner, a pallet will feed various sized groups from 18 soldiers for 16 days, to 288 soldiers for 1 day, which simplifies the logistics of field feeding."
One shortcoming that has been identified by the present inventors with the above-described self-heating group meal concept is the water delivery system comprising the fold-out reservoir and the single piece of continuous tubing connected thereto for delivery of water to the four heating trays. The present inventors have found the fold-out reservoir to be cumbersome and hard to use. In addition, the present inventors have found the single piece of tubing to be difficult to use since the tubing has to be positioned relative to the four trays so that four water outlet holes formed in the tubing are correspondingly aligned with the four trays. Moreover, because the single piece of tubing physically interconnects the four trays, one must cut the tubing between each pair of adjacent trays if one wishes to gain access to the contents of the lower tray of each pair.